Viruses are known to exert an oncolytic effect on malignant cells and the use of oncolytic viruses as therapeutic agents has been reported (Csatary et al. Cancer Detect Prev (1993) 17(6):619–27; Csatary et al. Anticancer Research (1999) 19(1B):635–8 and for review see Sinkovics J. of Clinical Virology (2000) 16: 1–15).
Oncolytic viruses, for example the avian virus Newcastle Disease Virus (NDV), have been shown to be cytolytic to tumor cells in vivo and in vitro (Reichard et al. J Surg Res (1992) 52(5):448–53; Bar Eli et al. J Cancer Res Clin Oncol (1996) 122: 1–7 and Tsadok-David et al. (1995) J. Cancer Research Clinical Oncology 121:169–174).
The Newcastle disease virus is an avian RNA paramyxovirus that causes Newcastle disease in different avian species (dependent on the virulence of the virus strain and on the age of the individual bird), but that is considered minimally pathogenic in humans. NDV is an enveloped virus containing a linear, non-segmented, single-strand, negative sense RNA genome. The virion consists of a coiled nucleocapsid containing single stranded RNA and 6 structural polypeptides (M.W. 20,000–80,000). The nucleocapsids are coated with protein and lipid envelopes. The matrix protein (M), located in the inner surface of the viral envelope, is involved in viral assembly and interacts with both the viral membrane and the nucleocapsid proteins. On the outer surface of the viral envelope are two viral glycoproteins: the hemagglutinin-neuraminidase (HN) and the fusion glycoprotein (F). The HN glycoprotein is involved in the binding of the virus to cellular receptors. Monoclonal antibodies raised against this protein were shown to neutralize NDV infectivity. The F protein, which is first expressed as an inactive precursor (F0) and then cleaved post-translationally to produce two disulfide linked polypeptides (F1 and F2), is involved in penetration of NDV into host cells by facilitating fusion of the viral envelope with the host plasma cell membrane. Antisera to the F protein inhibited hemolysis and virus-induced cell fusion Since the F and HN glycoproteins play a crucial role in NDV infectivity, much effort has been done to clone NDV genes. EP Patent 227414 to Bingham et al., discloses the cDNA sequence encoding the F and HN polypeptides of NDV Beaudette C strain and envisages the use of this nucleotide sequence for the preparation of labelled probes, which will be utilized for diagnosis of NDV in poultry as well as for the preparation of the F and HN polypeptides.
The state of proteolytic cleavage of the surface glycoproteins F and HN is responsible for the virulence of the different NDV strains. F0 of virulent strains is cleaved to F1 and F2 in a wide range of host cells, whereas F0 of avirulent strains is cleaved only in few host cells. Accordingly, these differences are expressed in the classification of the different strains of NDV as velogenic (highly pathogenic), mesogenic (intermediate in pathogenicity) and lentogenic (apathogenic) strains.
In addition to their role in infectivity, the HN and F surface glycoproteins of NDV have also been postulated to be involved in the oncolytic capabilities of NDV (MSc thesis by Alissa Waldman-Kegnovitch (1999) Dept of Virology, Haddasa Medical School of the Hebrew University of Jerusalem).
The effect of oncolytic viruses on neoplastic cells is attributed by some to the enhancement of the sensitivity of the neoplastic cells to the cytolytic activity of tumor necrosis factors and to the immune stimulatory properties of these viruses. NDV in animals induces locally chemokines and cytolines such as tumor necrosis factor alpha that affect T cell recruitment and activation (Schirrmacher et al. (1998) Semin Oncol 25(6):677–96 and Schirrmacher et al. (1999) Int J Oncol 14(2):205–15). There are other reports that attribute the killing effect of an attenuated strain of NDV (73-T) on neuroblastoma cells to direct cytolysis following replication of infectious virus (Lorence et al. J. Nat. Cancer Inst. (1994) 86(16) 1228–1233). The killing effect of a mesogenic strain of NDV (RO) on Daudi lymphoma cells and the effect of NDV Ulster strain on metastatic Esb lymphoma and B16-F10 melanoma was found to be unrelated to viral replication since UV inactivated viruses were found to be as effective as infectious viruses in killing these tumor cells (Tsadok-David et al. (1995) J. Cancer Research Clinical Oncology 121:169–174 and Schirrmacher et al. (1997) Clin Cancer Res 3(7):1135–48).
Present efforts at cancer therapy using viruses involve the use of live pathogenic viruses as cytolytic agents (see Csatary et al. above and U.S. Pat. No. 5,602,023 to Csatary). WO 00/62735 of Pro-Virus discloses the use of any interferon sensitive strain of virus for killing neoplastic cells that are deficient in the interferon response. The Pro-Virus disclosure supplies a catalog of viral strains including three mesogenic strains of NDV (MK107, NJ Roakin, and Connecticut-70726) shown to be useful for treatment of human tumor xenografts in athymic mice. NDV administration to these mice caused tumor regression, which was attributed to more efficient and selective replication of NDV in tumor cells versus normal cells. The differential sensitivity of tumor cells to killing by NDV was disclosed to be correlated to an inability of the cells to manifest interferon-mediated antiviral response. The above patent application claims methods of infecting neoplasms or tumors and methods of treating neoplasms or tumors by interferonensitive, replication competent RNA or DNA viruses
Alternative methods are mostly directed at developing vaccines for anti tumor immunization. For example, NDV is used in the preparation of an autologous tumor cell vaccine for humans (reviewed in Schirrmacher et al. (1998) Semin Oncol 25(6):677–96).
Nowhere in the background art is it taught or suggested that lentogenic strains of NDV are used for cancer therapy, or that surface glycoproteins derived from different strains of NDV, namely, velogenic, mesogenic or lentogenic strains, may have oncolytic properties and be useful in the treatment of cancer.